The aim of this project is to study the effects of antigens, antigen-antibody complexes and anti-idiotypic antibodies on the synthesis and secretion of antibody by differentiated antibody forming cells (AFC). Two types of AFC will be used: 1) continuous lines of AFC, such as myelomas with defined antigen binding activity and 2) antigen-derived AFC, elicited by immunization. Functional studies will be accompanied by analysis of antigen receptors and Fc receptors on the surface of AFC. The ability of antigens, immune complexes, and anti-idiotypic antibody to inhibit immunoglobulin production in vitro will be tested by culturing AFC with these ligands and measuring intracellular and secreted antibody. The specificity, kinetics and reversibility of inhibition will be examined, and the role of antigen and Fc receptors evaluated. Using myeloma cells, the mechanisms of inibition will be studied along the following lines. The fate of ligand-receptor complexes and effects of ligands on intracellular localization of antibody will be analyzed by immuno-electronmicroscopy. The level of inhibition (i.e. synthesis, assembly, or secretion of antibody) will be studied by polyacrylamide gel electrophoresis. The relationship between the cell cycle, expression of surface receptors and suppression of antibody production, will be analyzed in synchronized cell cultures. Parallel studies on receptor expression and antibody secretion will be done to delineate the pathways for membrane-bound and secreted immunoglobulins. AFC harvested at different phases (peaks, declines) of primary, secondary, and cyclical antibody responses will be examined for inhibition by antigens and antigen-antibody complexes in order to determine the role of such inhibition in the physiological regulation of humoral immune responses.